Plant out dahlias

The dahlia tubers I re-started earlier in the spring have grown well and are now ready to go out into the garden. Late May is the perfect time as the frosts are pretty much over and evenings are warmer.

In colder, exposed areas you may still get a ground frost, but the plants should survive if their roots are generously mulched and their foliage is covered with a couple of layers of fleece on the coldest nights.

In the step-by-step below I show you how to plant straight into a border. If you want to grow your dahlias in containers, plant them to the same depth as their rootball in multi-purpose compost enriched with a slow-release fertiliser.

When planting in a bed, site your dahlia in a sheltered sunny spot and insert a supporting cane next to it before it starts to grow.

Water well at planting and keep the soil moist while the plant gets established – a weekly drenching will keep plants healthy during dry spells.

Around a week after planting, feed with an organic fertiliser such as blood, fish and bone. Once the plants grow to 16in (40cm), pinch out the growing tips to encourage branching stems.

Dahlia earwig trap

Several pests will attack dahlias, including earwigs that will eat flowers and leaves. To catch them, up-end a plant pot stuffed with newspapers on a cane next to the plant. The earwigs crawl into it at night and can be removed in the morning.

Step by step

Getting your dahlias in the ground

1 Dahlias like free-draining soil, so if yours is heavy clay improve it by digging in plenty of grit or well-rotted manure or compost.

2 Dig a hole as deep as, and slightly wider than, the dahlia’s container and enrich the soil with bone meal to improve flowering.

3 Place the dahlia in the hole after teasing out any congested roots. Infill around it with soil and compost and firm it in. Water well.

Top tip

To get larger dahlia flowers, restrict the number of flowering stems to 3-5 per plant. For more, smaller blooms let the plant develop 7-10 stems. Deadhead regularly.